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Protection by prosaposin against ischemia-induced learning disability and neuronal loss
1Department of Neuropsychiatry, Ehime University School of Medicine, Japan.
Insights
Prosaposin infusion protected gerbils from learning deficits after brain ischemia. This neurotrophic protein preserved hippocampal neurons and synapses, suggesting a protective role against ischemic damage.
Area of Science:
- Neuroscience
- Biochemistry
Background:
- Prosaposin is a precursor to saposins, which activate sphingolipid hydrolases.
- Prosaposin is found in high concentrations in brain regions like the hippocampus.
Purpose of the Study:
- To investigate the neuroprotective effects of prosaposin against ischemic brain damage.
- To determine if prosaposin can prevent learning disabilities induced by forebrain ischemia.
Main Methods:
- Gerbils received continuous prosaposin infusion into the lateral ventricle for 7 days, starting before induced forebrain ischemia.
- Learning ability was assessed using the step-down passive avoidance task.
- Hippocampal neuron and synapse density were evaluated using light and electron microscopy.
Main Results:
- Prosaposin infusion almost completely prevented ischemia-induced learning disability.
- Infused gerbils showed significantly higher numbers of hippocampal CA1 pyramidal neurons and associated synapses compared to controls.
- Microscopic analysis revealed preservation of neuronal and synaptic structures in the prosaposin-treated group.
Conclusions:
- Prosaposin exhibits significant neurotrophic activity.
- Prosaposin effectively protects hippocampal CA1 neurons from lethal ischemic injury.
- These findings highlight prosaposin's therapeutic potential in mitigating ischemic brain damage and associated cognitive deficits.
Abstract:
Prosaposin, the protein precursor of saposins A, B, C, and D which activate sphingolipid hydrolases, is abundant in several brain regions including the hippocampus. We infused prosaposin continuously for 7 days into the lateral ventricle of gerbils starting 3 hours before 3-min of forebrain ischemia. Using the step-down passive avoidance task, we demonstrated that ischemia-induced learning disability is prevented almost completely by prosaposin infusion. Subsequent light and electron microscopic examinations showed that pyramidal neurons in the CA1 field of the hippocampus as well as synapses within the strata moleculare, lacunosum/radiatum and oriens of the field were significantly more numerous in gerbils infused with prosaposin infusion than in those receiving saline infusion. These findings suggest that prosaposin possesses neurotrotrophic activity to protect hippocampal CA1 neurons from lethal ischemic damage.